The rate of regrowth of the meniscus was compared after medial and lateral meniscectomies. Articular cartilage ulcers were observed 21 days after lateral meniscectomies and femoral pitting was observed after either procedure. Histologically, lesions were observed only after the lateral procedure. Regrowth of the meniscus was evident within 1 week of surgery as increased 3H-thymidine uptake and increased collagen synthesis by meniscal tissue from both surgical groups. These parameters returned to normal sooner after the medial than the lateral procedure. The excised meniscus was completely replaced by new tissue within 3 weeks of either procedure. In conclusion, the meniscus heals quickly following surgery and the small differences in the rate of regrowth between the two procedures do not seem to be adequate to explain the significant differences in femoral and tibial lesions.